Cannabis (drug) cultivation

Cannabis cultivation is the cultivation of the cannabis plant. Species of the Cannabis genus include C. sativa, C. indica, C. ruderalis, and "C. hybrids". Cannabis is grown for a variety of purposes, including as a source of materials for use in various products, such as food, clothing, cosmetics and fuel and for the production of cannabis material (or marijuana). This article, however, concentrates on cultivation of the latter. Cultivation techniques for other purposes are very different: see Hemp.

The drug material is used medicinally, recreationally, and spiritually, but its use is mostly illegal. See: Legal issues of cannabis.

The legal status of marijuana has led growers to novel cultivation methods for implementation indoors (due to aerial surveillance), such as hydroponics, aeroponics (itself a form of hydroponics), as well as organic cultivation methods. Research into the production of cannabis for the drug marinol and other more profitable and marketable forms of cannabis based medicines has further pushed the envelope of cannabis cultivation in all forms of laboratory public and private.

The emphasis on advanced cultivation techniques, as well as the availability of hybrid strains (e.g. Northern Lights, Blueberry, NYC Diesel), is believed to be a factor in the increase in the overall quality and variety of commercially-available cannabis over the past few decades. However, it should be noted that well-grown heirloom strains (e.g. Thai, Colombian Gold, Panama Red) are – and have always been – as potent and flavorful as modern hybrids. The following covers the plant's entire growth, from germination to harvest.

Botany

Cannabis is a member of the family Cannabinacea, along with hops. Cannabis is an annual and usually dioecious, which means it has separate pistillate (female) and stamenate (male) plants. A shorter photoperiod (day length) towards the end of the growing season is generally required to induce the reproductive (sometimes called flowering or budding) phase of growth, however some cultivars of Cannabis are auto-flowering, which means that they will flower regardless of the photoperiod.

The leaves are palmately compound, with serrate leaflets. During vegetative phase of growth, there is one leaflet on the first true leaf, three leaflets on the second, five on the third, and so on, up to about seven for Cannabis indica, and eleven for Cannabis sativa. The phyllotaxy reverses during reproductive phase, with bud leaves initially containing seven to eleven leaflets, and progressing down to one leaflet, and ultimately none at the terminal bud. Leaf arrangement is opposite during vegetative phase, and alternate during reproductive phase.

Plants are known for their production of oils, fibers, and psychoactive compounds known as cannabinoids, including the chemical tetrahydrocannabinol, or THC.

There are three different species in the genus Cannabis. These are Cannabis sativa, Cannabis indica, and Cannabis ruderalis. Generally only special low-THC cultivars of Cannabis sativa are used for industrial/agricultural purposes. For recreational or medicinal purposes, high-THC cultivars of both Cannabis sativa and Cannabis indica are used, as well as hybrid cultivars of both species, and even a few hybrids that allegedly contain some Cannabis ruderalis genetics.

Cultivation of the plant typically focuses on production of one of its above-noted ingredients. It is possible to grow the plants in a very close matrix, whereupon the resultant plants will have very fine fibers, which can be used to make fine cloth resembling silk. Alternatively, plants with select genetics, which are grown under close nutrient supervision and adequate lighting will produce higher quantities of THC.

While it is possible to grow cannabis simply for the purpose of a houseplant or as a hobby, the practice is quite challenging due to the need to keep the annual plant in a near perpetual vegetative state, which requires root pruning and artificial lighting for the winter months.

Traditional indoor cultivation

This section covers the traditional method of cultivating medicinal or recreational marijuana indoors, wherein the plants are grown in a soil-like medium and fertilizer is added when the plants are given water. Traditional outdoor cultivation techniques are covered in the next section, and alternative techniques, such as hydroponics and organic cultivation techniques, are discussed in the last section.

Cultivating marijuana indoors is more complicated and expensive than growing outdoors, but it allows the cultivator complete control over the growing environment, and will generally produce higher quality marijuana than plants grown outdoors.

Lighting

The single most important factor for the indoor cultivator to consider is lighting. A greenhouse would be ideal, but even these require supplemental lighting. Since cultivation of cannabis is harshly punished in most areas, many cultivators must set up a hidden indoor grow room and provide artificial light. Additionally, outdoor cultivators usually start their clones or seedlings indoors, under artificial light.

Fluorescent lighting

Fluorescent ballasts and bulbs are very inexpensive and much cooler and more efficient than incandescent bulbs. In marijuana cultivation, fluorescent lighting is useful for growing seedlings and rooting clones, because the light produced is very gentle (unlike HIDs, explained next), and won't burn young and/or sensitive plants. Fluorescents are available in 'warm' and 'cool' spectrums, with 'warm' providing more light in the red spectrum and 'cool' providing more light in the blue spectrum. Cultivators generally use 'cool' bulbs in order to encourage short internodes.

High-intensity discharge (HID) lighting

The best type of light to use for indoor marijuana cultivation is a High-intensity discharge lamp (HID). High intensity discharge lamps typically work by passing an electrical current through vaporized gas at high pressure, although low pressure sodium bulbs have gas at low pressure. There are many types of high intensity discharge bulbs, including mercury-vapor lamps, sodium vapor lamps, metal halide lamps, and conversion bulbs for metal halide and high pressure sodium.

The only high intensity discharge bulbs suitable for cultivating Cannabis are metal halide (MH) and high pressure sodium (HPS). There are bulbs available in many different wattages from 75 to 1500 watts, but marijuana growers usually only use between 250 and 1000 watt bulbs.

All high intensity discharge bulbs require a special ballast to run, which is contained in a metal box, which grows warm and hums quietly when in use. A metal halide ballast contains a capacitor and a transformer, and a high pressure sodium ballast contains a capacitor, a transformer, and an ignitor. Recently, electronic ballasts have also become available.

Most metal halide and high pressure sodium ballasts are not attached directly to the bulb socket, but rather are connected by a long cord. These are called remote ballasts, and allow the ballast to be placed in a different room from the bulb to reduce heat and clutter in the grow room. If a light has a ballast attached to the bulb socket, it is usually attached to the reflector as well, and it is called an enclosed ballast. Enclosed ballast systems are usually only available for smaller bulbs, generally about 250 watts or less.

While Cannabis will grow under most light spectrums, a full spectrum is best if possible. This is easy for the outdoor grower, as the sun produces a perfect spectrum of light. Unfortunately, neither high pressure sodium nor MH bulbs produce a full spectrum of light. It is best if both bulbs are used simultaneously, and some devoted hobby growers do, but this is rare in practice, and many people grow high-quality marijuana with just metal halide or high pressure sodium. Both bulbs have advantages and disadvantages, and produce different color spectrums.

=Metal halide (MH)

= Metal halide bulbs produce light that is strongest in the blue spectrum, technically about 4000 kelvins, or around 460 nanometers. Metal halide bulbs also come in various coated varieties intended to increase the red spectrum, but these are all inferior to a high pressure sodium in the red spectrum.

Metal halide bulbs produce about 65-115 lumens per watt and last up to 12,000 hours. They are available in vertical (BU or BD), horizontal (HOR), and universal (U), which may be burned either vertically or horizontally.

Metal halide is an excellent bulb for vegetative phase of growth, as it encourages short internodes (distance between sets of leaves), and inhibits cell elongation, creating a shorter, stockier plant. Growers with a single ballast often purchase a high pressure sodium ballast, and use a metal halide conversion bulb (a metal halide bulb designed for a high pressure sodium ballast) during vegetative phase.

Unlike high pressure sodium bulbs, metal halide bulbs also produce ultraviolet radiation, which may play a role in increasing the amount of THC produced by the plant.

=High pressure sodium (HPS)

= High pressure sodium bulbs produce light strongest in the red spectrum, technically about 2,200 kelvins, or around 660 nanometers.

High pressure sodium bulbs produce less heat and more light than metal halide bulbs, producing 97-150 lumens per watt, and they last longer as well, up to 24,000 hours.

High pressure sodium bulbs are excellent bulbs for the flowering phase, and the choice of most growers who have only one bulb. High pressure sodium bulbs are an excellent choice for the reproductive phase of growth, as they trigger a greater flowering response in the plant, and simulate a more autumn-like light spectrum. A high pressure sodium conversion bulb, a high pressure sodium bulb designed to be burned in a metal halide ballast, can be used during the reproductive phase if a grower has a metal halide ballast.

If high pressure sodium is used for vegetative phase, plants will usually grow slightly more quickly, but will also have longer internodes, and may be taller.

LED grow lights

Recent advancements in LEDs have allowed for the production of relatively cheap, bright and long lasting grow lights that emit only the colors of light required for plant growth. These lights are attractive to indoor-growers since they do not consume as much power, do not require ballasts, and produce a fraction of the heat of HID lamps.

The lamps consist of arrays of many wide-spectrum red and a few narrow-spectrum blue LEDs of specific wavelengths. Although LED grow lights have shown promise through plant research by NASA and many universities, it is unknown whether the results are applicable to Cannabis cultivation.

Light intensity

According to the inverse square law, the intensity of light radiating from a point source (in this case an HID bulb) is inversely proportional to the square of the distance from the source. So if an object is twice as far away, it receives only 1/4 the light. This is a serious hurdle for indoor marijuana growers, and many techniques are employed to use light as efficiently as possible.

= Reflectors

= Reflectors are the most important aspect of maximizing light efficiency. They come in two main types, designed to hold a bulb either horizontally or vertically. Most horizontal reflectors can be fitted with glass and air-cooled to reduce grow-room temperatures, and allow the bulb to be placed closer to the plants, although the glass panel slightly reduces light output. Water cooled reflectors are also available, but are rarely used, as they are very expensive and significantly reduce light output.

Vertical

Vertical reflectors are generally less practical than horizontal reflectors, as they are less efficient, although they are usually also less expensive. When a bulb is burned in a vertical position, most of the light is emitted sideways, and must be reflected downward towards the plant, which increases the distance that the light must travel.

Vertical reflectors are available in cone and parabolic dome shapes. Cone shaped reflectors are very inexpensive but also very inefficient, and are generally not used. If a vertical reflector is used, it is generally of the parabolic dome variety.

Horizontal

Horizontal reflectors are much more efficient than vertical reflectors, and generally more expensive. Most growers use horizontal reflectors, as the cost of a more expensive reflector is offset by the savings of burning fewer lights to generate the same light intensity at plant level.

Horizontal reflectors are available in a variety of shapes, most of which are roughly trapezoid shaped, although "bat-wing" or "gull-wing" designs are also relatively common.

= Wall covering

= Even with the most efficient reflectors and room layout, a lot of light is reflected on the walls of the grow room. In order to reflect this light back to the plants, marijuana cultivators cover the walls of their grow-room with some type of reflective material.

The most commonly used covering is 6 mil (150 µm) PVC plastic sheeting that is white on one side and black on the other. The plastic is installed with the white side facing in to the room to reflect light, and the black facing the wall, to reduce fungus and mold growth. Another common covering is flat white paint, with a high titanium dioxide content to maximize reflectivity.

Mylar sheeting is inexpensive and very reflective, and some growers swear by it, while others find that it distributes light too unevenly, or is too fragile. A more expensive but very effective option is a fabric called Foylon (Foil Laminated, Reinforced Reflection Fabric), which is about as reflective as Mylar, but is much more durable, has more even light distribution, and is easier to install and clean. If cold temperatures in the grow-room are a problem, a good choice is Astrofoil, which is about as reflective as Mylar, and is insulated to reflect heat as well as light.

= Light distribution

= When growing with artificial light, the light intensity will be very uneven in the grow-room. The plants closest to the light source will receive far more energy (in the form of photosynthetically-active radiation) than plants far away from the source. Additionally, plants will grow towards the light source (this is known as phototropism). In order to address this, many growers simply move their plants around within the grow room in order to ensure that all plants are growing evenly. This is easily facilitated by placing planters on casters.

Another option for the cultivator is to purchase a light mover. A light mover simply moves the light around within the grow-room, so that the plants will grow evenly without being moved, and also allows the bulbs to be placed closer to the plants. Light movers are available in two styles, linear and circular. Linear models have a motor which moves slowly along a rail in a straight line, suspended from which is a light. Circular models have a central motor which rotates two or three arms, from each of which is suspended a light. Circular movers generally allow the light to cover slightly more area.

Atmosphere

When growing indoors, the cultivator must maintain an ideal atmosphere inside the grow-room. The air temperature must be maintained within an ideal range, with a cooler night and warmer day, and adequate levels of CO₂ must be maintained in order for the plants to grow most efficiently. It is also important to promote vigorous air circulation within the grow room, which is usually accomplished by mounting one or more oscillating fans in the room, depending on its size. The elimination of the distinctive odor of flowering marijuana is of great concern to most cultivators as well, and they may employ several different methods to eliminate odor.

Air extraction and grow-room temperature

A common obstacle for the marijuana cultivator is reducing the high temperature in their grow-room, caused by the HID lights. An easy way to overcome this is to remove the hot air and replace it with cool air. In addition to growing warm, the air in the grow-room is rapidly depleted of CO₂, which plants need in order to carry out photosynthesis. The easiest way to maintain adequate CO₂ levels in the grow room is to remove the depleted air and replace it with fresh air.

Most cultivators solve heat build-up and CO₂ depletion simultaneously simply by using a powerful fan to extract hot, depleted air. Some growers also have a less powerful fan to force air into the grow-room, so that the extraction fan will run more efficiently.

= Ventilation fans

= There are four main types of fans employed by marijuana cultivators: axial fans, inline duct fans, exhaust blowers, and centrifugal fans. Axial fans are only used in small closet-type grows, as they can't move air through ducting.

Exhaust blowers are the most commonly used, and are very noisy, although also very powerful, and can operate at high static pressure, which is important to move air through long ducting and/or through carbon filters. Sometimes exhaust blowers are referred to as 'squirrel cage fans', named after the type of induction motor which drives the propellor.

Centrifugal fans are also very powerful, and operate at high static pressure, but are significantly quieter than exhaust blowers, and are also significantly more expensive. If ventilation noise is a concern, most cultivators will purchase a centrifugal blower.

Inline duct fans are a type of axial fan that is installed in a length of ducting. These are designed to be installed in long sections of ducting to help keep air moving from clothes dryers and the like, but are not very effective for ventilation purposes, and large numbers are required to move even a moderate amount of air. Additionally, they can handle only very low static pressure.

Odor control

One of the most common ways for an otherwise careful cultivator to be discovered by neighbors is by the distinctive smell emitted, especially during the reproductive phase of growth, by most strains of marijuana.

One of the most effective, and certainly the most common, way of eliminating odor is by forcing odorous air through a carbon filter. Many cultivators simply attach a large carbon filter to their air extraction system, thereby filtering any smell before the air is expelled from the grow-room.

Another way of eliminating odor is by installing an ozone generator in the extraction ducting. The air is forced past the ozone generator by the extraction fan, and the odorous air is neutralized as it mixes with the ozone. Cultivators must be sure that the air is thoroughly mixed before it is expelled outside, lest some odor escape.

Carbon dioxide enrichment

Assuming that adequate light levels are present in the grow room, the limiting factor in plant growth is the level of carbon dioxide (CO₂). Plants grown with supplemental carbon dioxide will grow more quickly, have larger stomata, and can utilize more light. There are two chief tools for increasing carbon dioxide levels in the grow-room: bottled carbon dioxide, and carbon dioxide generators.

The most common way to enhance carbon dioxide levels is by purchasing tanks of compressed carbon dioxide, and releasing it into the atmosphere of the grow room. To do this, the cultivator must purchase a regulator, an emitter, and a tank of compressed carbon dioxide gas. When this tank is empty it can be refilled inexpensively at a beverage supply or welding shop.

Another way to enhance carbon dioxide levels is with a carbon dioxide generator. A carbon dioxide generator is the most cost effective in the long run, but they are initially expensive. They also generate additional heat and moisture in the grow-room. Carbon dioxide generators work by burning either propane or natural gas, and typically have four to eight burners. Propane powered generators use the same type of tank as a gas grill, and natural gas burners can be attached directly to natural gas lines.

The least expensive and perhaps simplest given the required items is the milk jug and yeast solution. Put about five or six cups of sugar in a clean one-gallon plastic jug. To this add about a half gallon of water. Mix until the sugar is dissolved and add a little bit of active yeast. Poke a small hole in the lid and replace it on top of the jug.

Once a day, or as often as possible, shake the jug to thoroughly mix the contents. In a day or two the yeast will begin to grow and CO₂ gas will be a by-product in the jug. Once the yeast begins to grow, the shaking of the contents will produce a gaseous eruption through the hole in the lid. On its own, the device will slowly produce CO₂ as long as there is enough sugar in the mix and the yeast stays active. The daily shaking stimulates the mix to produce a surge of CO₂ gas. Therefore, the more times the jug is shaken, the more surges of CO₂ that will erupt into the room. The mix will need to be changed or refreshed every two to three weeks. This system should be more than adequate and perfectly safe for smaller grow spaces (twenty square feet or less). It is also very inexpensive to configure and maintain. This method is actually a very crude method of alcohol production as well, so other economies of colocation may be accomplished with regard to homebrewing.

Baking soda and vinegar can also be used. A balloon can be filled out of a 2-liter bottle and released in an enclosed grow area or into a bag around the plant. A simple bowl in the grow space works too.

Details of other methods and more detail on these methods can be found at The CO₂ enrichment guide

Germination

Seeds may be germinated in a variety of ways. One of the most popular is the paper towel method. Start by saturating several sheets of paper towels with water, then placing the seeds inside. The best source of water should be used such as filtered, distilled or spring water. Chlorinated municipal water should be avoided. 5-10ml of water per sheet of paper towel is sufficient. Typically, the paper towel (with seeds) is placed in between two plates, or in a bowl covered with plastic wrap, or in a ziplock freezer bag, to keep the paper towel from drying out. The germinating seeds are then put in a warm (not hot) area, such as on top of a radiator, water heater closet, or above warm lamps and are usually left for no longer than 24 hours. The optimal temperature is between 75 and 85 ºF (24–29 °C). Indicas will germinate with lower temps while sativas will need higher temps. Pure tropical sativas will need germination temps of 85 to 95 ºF (29 to 35 °C). Temps over 95 ºF (35 °C) will cause thermal death of most seeds. If the container is not light-proof, and it is in an area exposed to light, it should be covered with black paper or something opaque to keep out light. The seeds should be checked about twice a day, misting with water if the paper towel is too dry. Old seeds and less vital seeds should be rinsed once daily and placed in a fresh moist paper towel to prevent the spread of germination inhibiting bacteria. When a small white root emerges from the seed, tweezers may be used to plant the seeds in a growing medium. This method is not tricky, but if the paper towel is allowed to dry too much, the seeds may never germinate. Seeds should be placed in a neutral soil (minimal fertilizers). Placing the seed with the root tip facing up, down, and sideways each have its advantage. If the root tip faces up, the plant will develop an initially strong root system. If the root tip faces down, the plant will sprout more quickly. Placing the seed with the root tip facing sideways is a compromise of these options. When transplanting the freshly sprouted seed a light sprinkling of soil (just enough to cover the seed) is sufficient, with a few more drips of water to moisten the seed.

One of the easier ways to germinate cannabis seeds is by placing them in a cup filled with room temperature water. The cup is then placed in a dark area. Good (usuable) seeds will root on average anywhere between 12 and 48 hours.

Another easy method of germinating cannabis seeds involves the use of Jiffy Pellets. These are dry, compressed pellets of sphagnum peat moss that expand to cylinders with a height of about 3-4 cm when saturated with water. The cannabis seeds are then planted in the Jiffy Pellets, where they germinate as if planted in soil. This has the notable advantage of not requiring the transplanting of fragile seedlings, as the saturated pellets with their seedlings can be planted directly in the intended growing medium with a minimum of trouble and effort.

Vegetative phase of growth

When true leaves have formed, the plant begins the vegetative phase of growth. During the vegetative phase of growth, the plant directs its energy resources primarily to the growth of leaves, stems, and roots. A strong root system is imperative, as it is required for strong floral development. A plants needs 2 or 3 months to mature before blooming. The plant is ready when it has revealed its sex.

During the vegetative phase of growth, cultivators generally employ an 18 to 24 hour photoperiod, as the plants grow more quickly if they receive more light, although a warmer and cooler period are required for optimal health. While no dark period is required, there is debate among cultivators as to whether a dark period is beneficial, and many continue to employ a dark period.

Marijuana cultivators employ fertilizers high in Nitrogen and Potassium during this stage, as well as a complete micronutrient fertilizer. The fertilizer is generally mixed with water, and then applied to the plants, usually every other or every third watering. The cultivator must avoid over-fertilizing the plants, especially when they are young, or the plants will suffer from nutrient burn. As the plants grow larger and stronger, they are able to tolerate a stronger nutrient solution, and the strength of the fertilizer is gradually increased.

The modification of a plant's growth habit is called training. Indoor cultivators employ many training techniques in order to encourage shorter plants and more dense canopy growth. For example, unless the crop is too large to be extensively pruned, cultivators will remove adventitious growth shoots, often called suckers, that are near the bottom of the plant and/or receive little light and will produce poor quality buds.

Many cultivators also employ other techniques:

Topping is done by removing the top of the apical meristem (dominant central stem), called the apex or terminal bud, in order to transfer apical dominance (the tendency for the apex to grow more rapidly than the rest of the plant) to the shoots emanating from the two nodes immediately beneath the pruning cut. This process can be repeated on one or both of the two new meristems, when they become apically dominant, with the same results. This process can actually be repeated almost infinitely, but over-diffusion of apical dominance will produce smaller, lower quality buds, so it is usually done no more than a few times. Topping also causes more rapid growth of all of the branches below the cut while the plant heals.

Pinching is similar to topping in that it causes the lower branches to grow more rapidly, but the apical meristem will maintain apical dominance, which is especially useful if the plant has already been topped. Pinching is performed by firmly pinching the apical meristem(s) so as to substantially damage vascular and structural cells but without totally breaking the stem. This will cause the lower limbs to grow more rapidly while the pinched tissue heals, after which time the stem will resume apical dominance.

Reproductive/flowering phase of growth

The plant will be induced to flowering by decreasing light from 18-24 hours a day to dark cycles of 11-12 hours that simulate the oncoming winter in the fall as the days grow shorter. As a consequence, it works out well indoors to have two separate areas; one that is used for the initial vegetative state and one that is used for flowering and fruiting. It is mandatory to keep the dark cycle for flowering very dark with no light interruptions, as any light can stall flowering by days or weeks. Flowering generally lasts from 50 to 90 days indoors, if growing outdoors it may take somewhat longer, depending on the natural onset of the colder seasons.

Once a plant is big enough to mature, dark periods are required for most plants to flower and bear fruit. This will require putting the lamp on a timer, to create regular and strict dark periods of uninterrupted light. If growing in a greenhouse, the same effect can be created in the Summer (long days) by covering it with a blanket to make longer night periods. For example, a strict schedule of covering the plants at 8pm and uncovering them at 8am for 2 weeks will start your plants to flowering. After the first 2 weeks, the schedule can be relaxed a little, but it will still be necessary to continue this routine for the plants to completely flower without reverting back to vegetative growth.

If bloomed indoors the ideal height is 10 centimeters for sativas and 40-50 centimeters for indicas. Which takes 3-7 days and 14-21 days respectively. Plants are kept small but maturation is optimal, by using as much plants as you can, the optimal harvest can be achieved in the least time.

Outdoors, in spring and autumn, the nights are sufficiently long to induce flowering at all times. If possible, merely bringing the plants from indoors to the outside at these times will permit natural flowering.

A few weeks after reducing the light, many white pistils will begin emerging at every grow tip on the plant. These are the flowers; once you feel satisfied with the number of sprouted flowers, decrease the lighting schedule again to roughly 8-10 hours, simulating late autumn, the time when the cannabis plant reaches maturity and is completely ready for harvest.

Nutrition

Flowering plants should be given high phosphorus plant food and with little or no light in the dark cycle. 13 hours light, 11 dark for instance may increase flower size while still allowing the plant to go into the flowering mode. Use longer dark periods to speed maturity toward the end of the flowering cycle if time is of the essence. Doing this will however reduce total yield.

Perpetual harvest

Two shelves can be used, one identical to the other, if strictly indoor gardening is desired. One shelf's lights are set for 12-13 hours, and one is lit continuously. Plants are started in continuous light, and are moved to the other shelf to flower to maturity after several weeks. This flowering shelf should be bigger than the "starting" or "vegetative" shelf, so that it can accommodate larger plants. Or, some plants can be taken outside if there is not enough space on the flowering shelf for all of them near harvesting. By using mothers and cuttings, you could harvest 400 grams every two months using one lamp of 400W.

Traditional outdoor cultivation techniques

When cultivated outdoors, the chosen areas are those which receive twelve hours or more of sunlight in a given day. Northern locations are preferred (Humboldt County, California and British Columbia being particularly notable), but southern locations (such as Maui, Hawaii) are also known to be good producers.

In general, a south facing exposure is preferred for maximum sunlight exposure. In instances where the local laws do not permit growing cannabis, cultivators may choose to grow in forests or rugged and rural areas where the local population are not likely to find the crop. Another technique is to grow cannabis in a crop that is larger and obscures the plants, such as maize. This is reported by the United States government to be common in the midwestern states. Bamboo and elderberry make excellent camouflage companion plants.

Some government organizations have claimed that in state and national parks, people have been injured by these "rebel farmers" protecting their crops, including a well documented developing problem with Mexican cartels growing cannabis in US national parks and forests.

Harvest and processing

Ideal harvest timing

Buds are typically harvested when fully ripe. Generally, ripeness is defined as when the white pistils start to turn dark yellow, orange, light to mid red, etc. and the trichomes, "crystals", barely begin to turn milky from clear. These trichomes can range from completely clear (generally deemed underdeveloped, which yields more of a 'head-rush/uppity'), to amberish-red (which generally yields more of a 'body' high more commonly referred to as 'couch-lock'). Ideally, professionals will use a decent power magnifying glass, a brix meter (to measure "sugar" content), and a microscope. The potential seed pods swell with resins usually reserved for seed production, thus improving the quality of the buds (called colitas), which will swell to form full "colas". If harvested early on with only a few of the pistils turned color, the buds will have a more pure THC content and less of the cannabinoids CBD and CBN. The later psychoactive substances will create the bouquet of the marijuana, and influence the overall nature of the high from anywhere from purely psychedelic to purely sedative.

When harvesting buds, avoid touching the flowers, as the trichomes (pictured right) are fragile, and may break off. Completely cut the stalk of the plant, hang it upside-down in a cool, dark, dry place such as a sealed and climate controlled drying area.

Contrary to sensimilla (bud production focused cultivation), seeds are harvested when fully developed and often after the accompanying buds have begun to deteriorate. In contrast, hemp grown for fibre is harvested before flowering, and cannabis grown for cloning is not flowered at all.

Drying

The plants should be dried slowly over 2-4 weeks at roughly room temperature (24 Celsius). Keep the temperature stable for cannabinoids to preserve best. Flowers are hung by their stalks, allowing the internal fluids of the plant to remain in the flowers. Remove all of the roots and avoid getting soil on the buds. When the stems in the middle of the largest buds can be snapped easily, the plant is dry enough to be cured. Drying should be done in a dark place, as trichomes will deteriorate if exposed to light. Air must be removed often. Do not use heaters.

Curing

The curing process continues breaking down sugars and helps develop taste and more smooth smoke. Usually, the dried product is packed (not compressed) into glass canning jars which are airtight. Initially the product must be checked periodically (every few hours) to make sure the herb was properly dry and has not remoistened itself. If it has, it needs to be removed and further dried. After a couple of days, when the product is satisfactorily dry, the jars can be sealed off and opened just once a week. Curing is highly varied—the minimum is usually two weeks. Some growers even cure as long as six months, while others do not cure at all. Well-cured cannabis is, in general, a higher quality product and more pleasant to smoke. For the same reasons as when drying, curing jars should be stored in a cool, dark, place.

Recently, a new method of curation has developed called water curing. This method is preferred by people that usually do not have enough time, or simply do not want to wait very long for a finished product. This traditionally involves submersing the buds in water for a period of 7 straight days, while changing the water after each day (generally done by using a cooler with drainage). The buds are then dried (most quickly via a small combi-oven few minutes) and are ready to use. Water curation has an advantage that traditional methods do not. Nutrients can be added to the plants up until they are harvested. The water will flush out harmful chemicals (such as the ones used to feed the plants) as well as proteins, sugars, pigments and some resins. This will also increase the THC to weight ratio upwards of 30%. ^*

Hash

Hashish. Hashish can be produced by several methods. The method most employed in the West is to take the plants or flowers and beat them against a screen. This causes the trichomes to break off the plants, and be collected under the screen, which serves as a crude filter. In the East, in large outdoor grows, workers wearing leather coats run among the dense plants, and then like bees gather the pollen and trichromes off of their limbs, pressing it into shapes.

Bubble hash. One of the most preferred forms of hashish production is via the use of a bubble hash bag kit. After a harvest, there are typically many green leaves- particularly large shade leaves- which themselves cannot be smoked, but have collected over time many fallen trichromes. Rather than letting them go to waste, one takes these greens and soaks them in a bucket of cold water. The liquid is then passed through a succession of bags with decreasing screen sizes which capture the trichromes, which are then pressed into shape and let dry. The result is called bubble hash, due to the bubbling which occurs when it is heated for smoking. This bubbling is due to its purity, as adulterants tend to cause hash not to bubble. Though more expensive, bubble hash bag kits tend to pay for themselves in the long run. Many kits can be purchased over the internet. ^*

Hash Oil. Cannabinoids are soluble in some chemicals, notably butane. It is possible to take the leaves and stems of the plant, which are generally considered to be of low THC concentration, and immerse them in liquid butane. The butane is then captured through a filter, and evaporated (butane becomes a gas at room temperature, so one may simply allow it to evaporate). The resultant hash oil is often very strong in terms of THC content, which can be then smoked or added to foods. Note that one should not smoke or otherwise create flame in the presence of evaporated butane, which is highly combustible. Also be aware that butane is heavier than air and will settle on the ground. For this reason, hash oil should only be made outdoors.

Alternative cultivation techniques

Hydroponic cultivation

Increasingly popular, especially in the developed world, is the hydroponic cultivation of cannabis. Hydroponic cultivation generally occurs indoors, although there is no practical obstacle to growing outdoors. In general, it consists of a non-soil medium which is exposed to a nutrient and water flow.

There are many types of hydroponic systems. If the nutrient solution floods the loose growing medium and recedes for aeration, this is an ebb and flow or flood and drain system. Systems that gradually drip solution onto the medium are drip systems. Systems that intermittently spray roots floating in air are called aeroponic systems. If aerated water runs down a channel lined with a film of rooting medium, this is a nutrient film technique system. A series of tubes intermittently running high flow nutrient solution into the tops of growing containers use a top feed system.

The main advantages of hydroponic systems are greatly increase aeration of plant roots, and increased real-time control of nutrient uptake. The latter fact means that hydroponic systems are decidedly more difficult to operate for the amateur or hobby grower, and over-fertilization is common, as there is no soil to act as a nutrient buffer, many growers now use coconut fibre as a soilless medium due to its high drainage and buffering capabilities, making it almost impossible to over-fertilize. Additionally, if a hydroponic system fails, the crop has a high probability of dying as the roots rapidly dry out (this is especially true of aeroponic systems). However, properly operated hydroponic systems, with other factors at an optimum, have been proven to outperform soil under the same environmental circumstances.

In marijuana culture, some believe that hydroponically cultivated marijuana can have fewer byproducts in the resultant smoke and ash, providing for a cleaner and healthier smoke. Of course, the veracity of such claims is suspect, as with proper pre-harvest flushing, and post-harvest drying and curing, there would be nothing to indicate an inherent difference in harmful content between soil and soilless mediums. This itself is controversial, as many growers/botanists believe any excess nutrients are broken down into sugars during the drying and curing processes, effectively killing the plant by starving it of nutrients.

Organic cultivation

Organic (a substance containing a carbon molecule, and that is or was a living organism), may be a misnomer when applied to cultivation of cannabis, though it is similar to the organic food movement in recent times. The methodology is superficially similar to the hydroponic methods, with the exception of tending towards soil and nutrients which are derived from organic sources. In general, these sources are items like guano. The use of soil (generally in buckets or heavy duty plastic bags) makes for a more natural cultivation process. However, the composition of the "organic" nutrients is strictly monitored by the manufacturers, and is usually printed on the container. For this reason, the supposed organic cultivation of cannabis, especially indoors, resembles other controlled cultivation methods where the intake of the plants is closely monitored. Organically grown marijuana gives a smoother smoke, supposedly because the flowers are free of heavy metals and other impurities that may occur in chemical fertilizers.

Screen of green

One of the techniques used in the cultivation of cannabis is referred to as screen of green or SCROG. This technique is so called because it involves training the plants to adapt to a wire mesh (similar in technique to an arbor). In so doing, one attains a great uniformity in the crop, and all plants attain near equal exposure to lighting. This is a system particularly adopted by hobby growers with limited height in their grow-area to grow big plants but not by commercial grow operations, because it is very labor intensive to train the plants to the screen, and requires an extended vegetative phase, although it allows for very efficient light use. This method also causes stems to grow much stronger and be able to bear more fruit.

Sea of green

In contrast to the "Screen of Green" methodology, Sea of Green (or SOG) growing depends on the high density of plants (as high as 60 per square meter) to create uniformity in the crop. In this technique, which is often grown in hydroponic media, only the colas of the plants are harvested. In the image to the right, geometric containers are visible. Such containers are used to enforce the geometric distribution of flowers and plant material, as well as their exposure to lighting and atmosphere. Sea of green is popular with commercial cultivators, as it minimizes the amount of time a plant spends in vegetative stage, and allows very efficient light distribution, keeping the plants much closer to the lights than when grown to full size.

Sinsemilla

A long tradition among cultivators of cannabis, sinsemilla (literally, "without seeds" in Spanish) is the product of removing male plants from the grow environment before they have a chance to fertilize the females. The resultant cannabis contains more psychoactive compounds in comparison to cannabis that has been grown in a pollinated environment. The reason for this is that the production of seeds requires an immense amount of energy, and if left unpollenated a female plant will divert all her energy in calyx production in an effort to catch pollen. This is especially desirable, as the calyx is where the highest concentration of trichomes exists, and the more densely packed a plant is with calyces, the greater psychoactive effect that plant will likely have.

Thus, sinsemilla is more expensive to purchase than cannabis with seeds, as the purchaser is actually receiving more psychoactive substance. Potent sinsemilla is especially important to medical users, to minimize the amount of cannabis they must consume in order to be afforded relief. Cannabis with seeds is generally considered to be of inferior quality and/or grown with inferior technique. A common term for seeded, or otherwise low-quality, cannabis is schwag, or "stress".

Genetics and breeding

Selection of mother plants

An important factor in cannabis cultivation is selecting the best genetics for one's crop. This is frequently done by selecting one or more known strains, or strains with preferred genetics (in the case of marijuana, one might use seeds from a batch that was particularly enjoyed), and then growing a number of the seeds to find out which exhibit the characteristics most desirable to the cultivator.

Plant characteristics which are generally selected for include:

Overall yield
Time to fruition
Resistance to pests
Geometric traits (uniformity, compactness, flower density, etc)
Color
Flavor and/or aroma
Appeal to end buyer (known as "bag appeal")
Psychoactive Qualities

When a cultivator has decided which plant or plants exhibit the most desirable traits, a cutting is taken and grown to maturity but never allowed to flower. This plant is referred to as a mother, and can be kept for a number of years, producing thousands of clones genetically identical to the mother.

Feminized seeds

It is possible to use a combination of cloning and "shocking" plants to get them to produce feminized seeds. A clone will retain the same sex throughout its life, so if a female plant is cloned, its clone children will also be female, precluding reproduction.

It is possible to use very erratic lighting, or several days of no light at all, to shock a plant into turning into a hermaphrodite. Such plants have both male and female sex organs. After doing this, a hermaphrodite can reproduce with one of its clone children. This will yield sometimes in excess of 90% female plants, if the process is begun with a female. This makes the cultivation of sinsemilla from seed much easier. It is very difficult to produce reliable feminized seeds, however, as plants grown from feminized seeds demonstrate a greater tendency towards hermaphrodism.

Hybrid vigor

When crossing two strains of cannabis (or two of any plant), the resultant hybrid may possess what is called hybrid vigor. In general, this produces a plant which is healthier, stronger, or quicker growing than its predecessors. Sometimes, in the case of a plant which has been brought back from fruiting (fruition, as mentioned above), it may be beneficial to cross it back with another (close) relative, in the hopes that it will become invigorated.

Caution should be exercised, as one does not always attain a beneficial cross with hybridizing.

Cloning from cuttings

Like many plants, cloning of cannibis is possible though technically more laborious and somewhat challenging, due to the cleanliness required. The process itself is quite similar to the cloning of most other plants and involves rooting branch cuttings from donor plants.

Cutting are taken and the large leaves near the bottom of the plant are removed to minimize transpiration and the cutting is allowed to heal before being immersed in a a dilute solution of high phosphorous fertilizer (10-50-10). While keeping the cutting under the solution, a 45 degree cut is made to the "root" end of the cutting using a clean knife that has been sterilized with bleach. This procedure prevents air bubbles from forming in the xylem of the stem which may effect water and nutrient uptake. Using a clean knife minimized infection and ultimately the death of the cuttings.

Rooting hormone gels or powder mixes are then applied to the cut to promote root growth and inhibit fungal infection. Growth trays with good drainage, filled with a moistened loose organic medium such as vermiculite and perlite is used allow the cuttings to root. Sterilization of the medium by baking or steaming is preferred. The cuttings are then inserted into the loose medium, and then must be continuously kept in a dim, moist, and humid environment under a plastic covering for up to two weeks such that they have a chance to heal and form roots. During the first week the cutting should not be watered unless the medium becomes dry, and even then, it should be done with discretion. A weak solution of high phosphorous fertilizer, usually sold as flowering promoting fertilizers, can be applied to the cutting in the second week since the phosphorus helps the rooting process, which will help in producing strong plants.

If performed correctly, the cuttings should stay green during their rooting time, and condensation should appear on the plastic coverings for the cuttings, which indicates proper humidity. Drooping and browning of the cuttings likely indicate too much sunlight, too little humidity, cutting rotting in sitting water, or unsanitary cloning conditions.

Detection and the law

As cannabis and its cultivation is illegal in most parts of the world, considerable resources are committed to the interdiction of cultivation.

Outdoors

Outdoor cultivation is common in both rural and urban areas, with outdoor cultivators tending towards growing sativa-based strains for better response to sunlight and reduced emission of odours.

Cannabis plants blend in easily with other plants to the point that they are unidentifiable by all but the most observant. Often simple camouflage techniques can avert detection, such as mixing in cannabis plants with other bushy, leafy species. Plants started outdoors late in the season tend to grow less tall, attracting less attention when placed next to plants of similar or taller stature. Even tall plants grown among trees can be almost invisible in their camouflage.

A common technique used by many outdoor growers is to dig a hole and put a potted plant in it. This reduces a plant's height by at least a foot, reducing its visibility to neighbours, visitors and guests. Also, some growers top the plant when it is only 12 inches (30 cm) high, and grow the 2 tops horizontally along a trellis. When using this technique, it is unlikely the plant will grow to be over 3 feet (1 m) tall.

Law enforcement agencies often monitor certain wider areas, particularly areas of countryside with a significant history of outdoor cannabis cultivation. Flying above in helicopters, they use infrared cameras and other equipment that can detect cannabis by measuring the heat and reflective signature of the vegetation below. Cannabis has higher reflectivity at certain wavelengths than other rural crops such as maize (corn). Law enforcement agencies have found that the use of this technology has become necessary in their detection efforts because many growers hide cannabis among other plants, making detection with the naked eye difficult even from the air. These techniques are effective and difficult to defeat because the reflective signature of a given type of plant is difficult to change or mask.

Indoors

Indoor growing has become increasingly common over the past decade, in part due to increased availability of equipment, seeds and instructions on how to cultivate. So-called grow-ops are seen by many marijuana enthusiasts as a much cheaper way in which to gain a steady, higher-quality supply of cannabis, also, on a larger scale they have proven a viable commercial venture with some law enforcement agencies finding grow-ops large enough to yield several kilograms of marijuana. More expansive grow-ops, however, are generally more susceptible to detection than smaller scale operations.

Since individual grow light power generally ranges from 250 watts to in excess of 1000 watts and remain lit for a long time each day, differences in utility bill costs are a significant security issue for growers. It is not uncommon for power companies to work with law enforcement if they witness significant increases in power usage relative to a household's previous electricity costs. Employing energy saving methods is a common way to alleviate this, for instance; switching off light bulbs when leaving rooms, purchasing energy efficient appliances, using TV's or computers less, buying lower power light bulbs and so forth.

Some strains, especially the cultivar Cannabis indica, can give off strong odors as they grow, resulting in tip-offs and eventually detection. Growers frequently use carbon scrubbers in conjunction with ventilatiion in order to control odors. This typically involves forcing air from the grow room through a device containing activated carbon, before being vented outdoors. Carbon scrubbers can be built relatively cheaply, but require routine replacement of the carbon materials to maintain maximum effectiveness. Another option is to use an ozone generator. Ozone reacts with odor molecules in the air, permanently eliminating them. However, ozone can build up to levels that may be hazardous both for the grower and the plant, so the machine is usually run on a timer for pre-set intervals of time. As a last resort, strong air fresheners can be used to control smells as well as keeping windows firmly shut. This is typically a risky method, as the smell of air fresheners may often arouse suspicion by police officers. Checking outside to see if any smells are emanating from indoors is often a necessary precaution, as many growers become acclimatized to the smell of their plants, and fail to realize just how pervasive the odor may be. In short, storing plants in more isolated areas such as a basement or attic can greatly help prevent smell detection. Another perhaps less obvious solution is to simply grow a strain which possesses a weaker odor.

Storing plants and lights away from windows and areas which may be seen by visitors is also a common practice. Keeping the entire grow op in the attic or basement can solve this problem. Some growers, finding this impractical, may cover their windows with light-resistant materials. This can solve the problem of escaping bright light but may arouse suspicion amongst neighbours and local residents.

Many cultivators face detection by fire. Fires normally originate from faulty electrical equipment or wiring. Shoddy fixtures and sockets, improperly grounded equipment, and faulty circuit breakers are some of the most prevalent causes. Due to the large amount of electricity needed for large-scale cultivation, old or damaged wiring is more prone to melt and short. Some commercial growers resort to power theft in order to hide electricity usage and many of these people do not take the necessary precautions to make sure their connections are safe. Mounting a nearby smoke alarm and keeping a properly rated fire extinguisher handy can provide cheap insurance. Many growers adapt light cycles so that the lights are on when they are home and off when they are away.

Another common source of fire is caused by plants making contact with hot HID bulbs. Checking growth daily and using a cool tube and quality fan can help eliminate this problem. Growers using fluorescent bulbs with reasonable air circulation should not have this problem.

Word of mouth can of course be as much a threat to growers as any of the above issues. Often, a few sentences of conversation overheard can result in a tip-off and thus speedy detection. It is for this reason many growers keep as quiet as possible about their cultivation.

References

Cervantes, Jorge. Indoor Marijuana Horticulture. Van Patten Publishing, 2001. ISBN 1878823299
Clarke, Robert Connell. Marijuana Botany. Berkeley: Ronin Publishing, 1981. ISBN 091417178X
Green, Greg. The Cannabis Grow Bible. San Francisco: Green Candy Press, 2003. ISBN 1931160171.
Herer, Jack. The Emperor Wears No Clothes: The Authoritative Historical Record of Cannabis and the Conspiracy Against Marijuana. Ah Ha Publishing Company,2000. ISBN 1878125028
Starks, Michael. Marijuana Chemistry: Genetics, Processing & Potency. Ronin Publishing, 1990. IBSN 0914171399

External links

Seedbank Update - The authority for seedbank market research.
HighGrow 4.20 - A freeware computer program to learn how to cultivate Cannabis.
Cannabis cultivation forums & strain guide

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